Tuning circuits



Jul 23, 1935. y B, TREVOR 2,009,212

TUNING CIRCUITS Filed Feb. 12, 1952 INVENTOR BERTRAM TREVOR ATTORNEY Patented July 23, 1935 UNITED STATES TUNING CIRCUITS Bertram Trevor, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 12, 1932, Serial No. 592,531

2 Claims.

This invention relates to signalling devices, and in particular to means for coupling, amplifying, relaying, translating, or rectifying tubes.

More in detail, this invention relates to an im- 5 provement in thermionic signalling systems in which the input electrodes of a tube are energized at alternating current potentials and its output electrodes are connected in two parallel circuits, one of which includes a choking inductance through which direct current potential is applied to the anode and the other of which includes a stopping capacity and a tuned inductance by means of which the signals relayed, amplified, or detected in the thermionic tube may be impressed on to the next thermionic stage for further amplification.

In the present thermionic repeaters or relays as briefly described above, considerable high frequency losses take place in the output circuit of the amplifier tubes due to the distributed capacity of the choking inductance through which direct current potential is applied to the anode of the tubes.

An object of the present invention is to reduce losses at radio frequencies from taking place in the choking inductance in the anode direct current circuit of the relay or amplifier.

In accordance with the present invention, this is attained by the use of two small choke coils spaced apart from each other in place of the single large choke coil used heretofore; The above arrangement of the two small choke coils present a lower distributed capacity than the single larger choke coil thereby giving lower high frequency losses. This results in a better tuned circuit where the choking inductance is used, as indicated above, in the output circuit of a tube having parallel portions, one of which is common to the input circuit of a succeeding tube.

The novel features of my invention have been pointed out in the claims appended hereto.

The nature of my invention and practical application thereof, and the operation thereof will be understood by the following detailed description, and therefrom when read in connection with the drawing in which the single figure illustrates a modification.

In the drawing a thermionic tube 2 has its control grid 3 and cathode 9 connected with any kind of a source of high or low frequency signals 6 which are to be relayed or repeated in tube 2. The anode 5 of tube 2 is connected through a pair of radio frequency choke coils RFC to the positive terminal of a potential source It] by means of which direct current potential can be applied to theanode 5. Screen gridelectrode 8 is maintained at a positive potential with respect to the cathode 9 by a lead l2 to the source it. The alternating current potentials appearing at 5, after being repeated in tube 2, are impressed through block- 5 ing condenser BC on the tuned circuit LC which when tuned to signal frequency impresses said oscillations on the input electrodes I3 and M of a following thermionic tube H. Since the output electrodes of tube II are coupled to the following repeater I5 in the same manner that tube 2 is coupled to tube II a description of said coupling is thought unnecessary. In arrangements known heretofore a single choking inductance has been connected between the anode 5 and the source l0 and/or the anode l6 and source In. By the use of two small choke coils-spaced apart from each other and electrically connected in series results in a much lower tuned circuit loss than has been heretofore obtainable.

In actual practice, applicant has found that in a receiver adapted to cover a range of 530 to 900 meters two SOD-turn choke coils, each of an inductance of 6.5 millihenries, giving a total of 13 millihenries, operated extremely satisfactorily and resulted in much lower frequency losses than obtainable heretofore. These specific values have been given for purposes of illustration and are not intended to limit the scope of the invention.

I claim:

1. In a high frequency signalling system comprising a plurality of thermionic tubes, the input electrodes of said tubes being energized by alternating current potentials, and their input electrodes connected in two parallel circuits, one of which includes a choking inductance comprising a pair of inductance coils adapted to cover a range of 530 to 900 meters, said inductance coils having an inductance of substantially 6.5 millihenries, and each coil connected in series between the anode and the cathode of another tube, a tuned inductance connected in parallel with the input impedance of another tube, a connection between the cathodes of both of said tubes, and a capacity connecting the high potential terminal of said tuned inductance to the high potential terminal of said choke coils.

2. In a high frequency signalling system comprising a plurality of thermionic tubes having a screen grid electrode, the input electrodes of said tubes being energized by alternating current potentials, and their input electrodes connected in two parallel circuits, one of which includes a choking inductance comprising a pair of inductance coils adapted to cover a range of 530 to v 900 meters, said inductance coils having an inductance of substantially 6.5 millihenries, and each coil connected in series between the anode and the cathode of another tube, a tuned inductance connected in parallel with the input impedance of another tube, a connection between the cathodes of both of said tubes, a connection from said screen grid electrodes to a high potential source so as to maintain said screen grid electrodes positive with respect to the said cathodes, and. a capacity connecting the high potential terminal of said tuned inductance to the high potential terminal of said choke coils.

BERTRAM TREVOR. 

